I will present some of our recent results on cross-correlation weak lensing of galaxy-clusters with the Sloan Digital Sky Survey's MaxBCG cluster catalog. These results demonstrate that weak lensing can be used to map out the average cluster profiles to high precision and detect many of the features predicted by CDM structure formation simulations. I will present a mass-richness calibration of clusters, as well as relations between mass and other properties such as halo concentration and halo bias with a focus on cosmological constraints. In addition, I discuss how these methods will be applied to future surveys such as the Dark Energy Survey, SNAP and LSST to constrain dark energy and probe the nature of dark matter and cluster physics.